Purchase fence lattice in the dimensions you desire. Since you are extending your fence upward, you will need fence lattice that is taller than the fence you already have. However tall you want your fence to be, buy the lattice with 2 extra inches in height since it will be shallowly buried in the ground.
Dig a 1-inch-deep ditch with the shovel along the border of your existing fence where you would like to extend it. The ditch should be the length of your fence lattice.
Use the level to make sure that you are building a ditch that is consistent in depth.
Place the fence lattice in the ditch and allow it to lie against your existing fence.
Use the level on the top of the fence, to ensure that it is entirely horizontal.
Place a screw through each of the lattice fence's four corners, using the electric screwdriver. This will secure it to the existing fence.
Fill in the ditch you dug at the fence's base.